CA1137520A - Method of hydrogenation of benzene to cyclohexane - Google Patents
Method of hydrogenation of benzene to cyclohexaneInfo
- Publication number
- CA1137520A CA1137520A CA000363803A CA363803A CA1137520A CA 1137520 A CA1137520 A CA 1137520A CA 000363803 A CA000363803 A CA 000363803A CA 363803 A CA363803 A CA 363803A CA 1137520 A CA1137520 A CA 1137520A
- Authority
- CA
- Canada
- Prior art keywords
- benzene
- hydrogen
- cyclohexane
- pressure
- hydrogenation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The subject of this invention is a method of catalytic hydrogenation of benzene to cyclohexane in gaseous phase on solid catalysts consisting of an active metal and/or oxide thereof, deposited on carriers. The essence of the invention is obtaining cyclohexane with suitable purity as a result of passing a mixture of benzene vapour and hydrogen, containing even a small, in relation to the stoichiometric composition, excess of hydrogen, successively through a catalyst bed containing platinum or palladium, and through a catalyst bed con-taining nickel. This makes possible a complete hydrogenation of benzene with a single evaporation of the raw material and without circulation of gases, whereby there are no limitations relating to the upper limit of pressure for conducting the method so that the pressure at which the hydrogen is supplied may be employed.
The subject of this invention is a method of catalytic hydrogenation of benzene to cyclohexane in gaseous phase on solid catalysts consisting of an active metal and/or oxide thereof, deposited on carriers. The essence of the invention is obtaining cyclohexane with suitable purity as a result of passing a mixture of benzene vapour and hydrogen, containing even a small, in relation to the stoichiometric composition, excess of hydrogen, successively through a catalyst bed containing platinum or palladium, and through a catalyst bed con-taining nickel. This makes possible a complete hydrogenation of benzene with a single evaporation of the raw material and without circulation of gases, whereby there are no limitations relating to the upper limit of pressure for conducting the method so that the pressure at which the hydrogen is supplied may be employed.
Description
This invention relates to a method of catalytic hydrogenating benzene to cyclohexane in gaseous phase on solid catalysts consisting of an active metaland/or an oxide thereof, deposited on carriers.
Cyclohexane is one of the most important intermediate products in the chemical industry, being especially useful in the preparation of monomers for producing polyamide fibres and plastics. Cyclohexane intended for further pro-cessing needs to possess high purity. The content of benzene should not exceed 0.01 % by weight. Cyclohexane is almost exclusively obtained by hydrogenation of benzene. There are known and utilized on an industrial scale methods of hydrogenating benzene in liquid and gaseous phase. The first mentioned methods do not, however, admit of obtaining cyclohexane meeting the requirements, since the hydrogenation reaction in liquid phase cannot be conducted to the end in conditions which could be economically employed in the industry.
Purification of cyclohexane from benzene is very expensive as a result of the proximates of the boiling and freezing points of said compounds. Por these reasons the hydrogenation of benzene to cyclohexane is, as a rule, con-ducted in gaseous phase, and in technological processes employing hydrogenation in liquid phase the product of hydrogenation is submitted to an additional reac-tion in gaseous phase in order to achieve a conversion of benzene of above g9 99 %-The hydrogenation reaction of benzene is highly exothermic, which in the case of gaseous yhase reaction causes strong overheating of the catalyst bed. As catalysts in the hydrogenation reaction of benzene on industrial scale most frequently metallic nickel is used, deposited on carriers, more seldom are used platinum and palladium on carriers.
A disadvantage of platinum and palladium catalysts is the necessity of the application of high pressure, of the order of several MPa, and of the need 1137S2~) for a relatively large excess of hydrogen in order to achieve the full conver-sion of benzene. Such factors are expenslve both with respect to high invest-ment outlays for compressors and apparatus, and high operational costs.
A disadvantage of nickel catalysts, instead, is the danger of the occurrence of methanation of the benzene after surpassing a determined tempera-ture threshold, generally of about 300 C. Thus, the process must be conducted such that the temperature within the catalyst bed does not exceed about 250 C, which requires the em~loyment of processes disadvantageous from an economic point of view. The overheating of the bed can be prevented by conducting the process at low pressure, e.g. 0.2 to 0.3 MPa. In such cases, however, a high excess of hydrogen must be used to obtain the required conversion of benzene.
A consequence thereof is the necessity of circulating hydrogen, and thus of the installation of compressors. Another method consisting in dilution of the stream of reactants by adding thereto a portion of the final product shows similar disadvantages. In the industry there is employed a method of two-stage hydrogenation of benzene consisting in which at the first stage benzene is hydrogenated at relatively low pressure, for instance 0.3 MPa~ and without an excess of hydrogen, so as to achieve a conversion of about 90 %. The reaction product is condensed out, separated from hydrogen, and evaporated at higher pressure in a stream of excess hydrogen, whereafter the mixture passes through the catalyst bed and the reaction comes to an end. The cyclohexane vapour is condensed out, and the gases are expanded and led to the first stage of hydro-gonation. Such a method does not require the gases to be circulated, but shows~
however, the following disadvantages:-necessity of expansion of a portion of the gases which had to be compressed previously, and low pressure of waste gases, which produces a very severe problem of removal of cyclohexane vapours there-from.
` ~37'520 Unexpectedly :it has IIOW been found that a very good conversion of benzene to cyclohex~me with no side-reactions can be achieved if the mixture of benzene vapour and hydrogen, containing, even only a slight, in relation to the stoichiometric composition, excess of hydrogen~ is passed through a catalyst bed containing a platinum or palladium catalyst and subsequently through a nickel catalyst bed, at a temperature of 100 to 300 C. The reaction temperature is to be understood as the temperature of the liquid cooling the catalyst bed without regard to overheating of said bed. In the first bed there can occur overheating of up to 350 C, being, however, not harmful for these catalysts, since the reaction of methanation of benzene does not occur to a substantial degree.
The conversion of benzene after the first catalyst bed is generally within the limits of 90 to 95 %. The gas stream, having the composition deter-mined by said value of conversion of benzeneJ passes onto the nickel catalyst bed. In spite of relatively high pressure, expressed in MPa, a strong overheat-ing of the bed does not occur because of the relatively small content of benzene in the mixture. Instead, the complete hydrogenation of benzene to cyclohexane occurs. Thus, unexpectedly it has been shown that, on nickel catalysts, as opposed to platinum and palladium catalysts, a conversion of benzene of 99.99 %
can be achieved already with small excess of hydrogen, the reaction rate being high. Such a result can be obtained if the partial pressure of hydrogen in the process amounts to even below 0.1 MPa.
Thus, the method of this invention avoids the disadvantages of hitherto known processes. Particularly, it makes possible a complete hydro-genation of benzene with a single evaporation of the raw material and without circulating the gases, whereby there are no limitations relating to the upper limit of the process pressure. This enables the process to be conducted at whatever pressure the hydrogen is supplied, and solves the problem of removal of ~ ~137S~(~
cyclohexane vapours from waste gases.
Both catalyst beds can be disposed either in separate reactors or in single reactor, the tubes of` which are filled with both catalysts in a ma~mer such that the reactant mixture passes first through the platinum or palladium catalyst and then through the nickel catalyst.
In the case of employing two reactors, it is preferable to apply in both the same process pressure, differing only by the values of the resistance of flow. Conveniently, the same process temperature can also be employed. Use of boiling water at a pressure of, for instance, 1.0 to 1.5 MPa as cooling water results in the production of heating steam of high quality. The reaction temperature will be equal to 180 to 200 C, not taking into account local over-heating of the bed to a higher temperature.
In an industrial realization of the process of hydrogenating benzene according to the method of the invention, the gases separated after condensing out the cyclohexane vapour can be, as a rule, discharged to the atmosphere.
If, however, in the process hydrogen is employed which contains con-siderable amounts of inert gases, then it is purposeful, but not necessary, to circulate said gases. The circulated amount can be small, since in the process according to the invention the partial pressure of hydrogen in the reactor can amount to for instance 0.1 MPa, whereas in known processes using platinum or palladium catalysts a partial pressure of hydrogen is required generally of above 2.0 MPa.
EXAMPLE I
A reactor built of a tube having a diameter of 32 mm and length of
Cyclohexane is one of the most important intermediate products in the chemical industry, being especially useful in the preparation of monomers for producing polyamide fibres and plastics. Cyclohexane intended for further pro-cessing needs to possess high purity. The content of benzene should not exceed 0.01 % by weight. Cyclohexane is almost exclusively obtained by hydrogenation of benzene. There are known and utilized on an industrial scale methods of hydrogenating benzene in liquid and gaseous phase. The first mentioned methods do not, however, admit of obtaining cyclohexane meeting the requirements, since the hydrogenation reaction in liquid phase cannot be conducted to the end in conditions which could be economically employed in the industry.
Purification of cyclohexane from benzene is very expensive as a result of the proximates of the boiling and freezing points of said compounds. Por these reasons the hydrogenation of benzene to cyclohexane is, as a rule, con-ducted in gaseous phase, and in technological processes employing hydrogenation in liquid phase the product of hydrogenation is submitted to an additional reac-tion in gaseous phase in order to achieve a conversion of benzene of above g9 99 %-The hydrogenation reaction of benzene is highly exothermic, which in the case of gaseous yhase reaction causes strong overheating of the catalyst bed. As catalysts in the hydrogenation reaction of benzene on industrial scale most frequently metallic nickel is used, deposited on carriers, more seldom are used platinum and palladium on carriers.
A disadvantage of platinum and palladium catalysts is the necessity of the application of high pressure, of the order of several MPa, and of the need 1137S2~) for a relatively large excess of hydrogen in order to achieve the full conver-sion of benzene. Such factors are expenslve both with respect to high invest-ment outlays for compressors and apparatus, and high operational costs.
A disadvantage of nickel catalysts, instead, is the danger of the occurrence of methanation of the benzene after surpassing a determined tempera-ture threshold, generally of about 300 C. Thus, the process must be conducted such that the temperature within the catalyst bed does not exceed about 250 C, which requires the em~loyment of processes disadvantageous from an economic point of view. The overheating of the bed can be prevented by conducting the process at low pressure, e.g. 0.2 to 0.3 MPa. In such cases, however, a high excess of hydrogen must be used to obtain the required conversion of benzene.
A consequence thereof is the necessity of circulating hydrogen, and thus of the installation of compressors. Another method consisting in dilution of the stream of reactants by adding thereto a portion of the final product shows similar disadvantages. In the industry there is employed a method of two-stage hydrogenation of benzene consisting in which at the first stage benzene is hydrogenated at relatively low pressure, for instance 0.3 MPa~ and without an excess of hydrogen, so as to achieve a conversion of about 90 %. The reaction product is condensed out, separated from hydrogen, and evaporated at higher pressure in a stream of excess hydrogen, whereafter the mixture passes through the catalyst bed and the reaction comes to an end. The cyclohexane vapour is condensed out, and the gases are expanded and led to the first stage of hydro-gonation. Such a method does not require the gases to be circulated, but shows~
however, the following disadvantages:-necessity of expansion of a portion of the gases which had to be compressed previously, and low pressure of waste gases, which produces a very severe problem of removal of cyclohexane vapours there-from.
` ~37'520 Unexpectedly :it has IIOW been found that a very good conversion of benzene to cyclohex~me with no side-reactions can be achieved if the mixture of benzene vapour and hydrogen, containing, even only a slight, in relation to the stoichiometric composition, excess of hydrogen~ is passed through a catalyst bed containing a platinum or palladium catalyst and subsequently through a nickel catalyst bed, at a temperature of 100 to 300 C. The reaction temperature is to be understood as the temperature of the liquid cooling the catalyst bed without regard to overheating of said bed. In the first bed there can occur overheating of up to 350 C, being, however, not harmful for these catalysts, since the reaction of methanation of benzene does not occur to a substantial degree.
The conversion of benzene after the first catalyst bed is generally within the limits of 90 to 95 %. The gas stream, having the composition deter-mined by said value of conversion of benzeneJ passes onto the nickel catalyst bed. In spite of relatively high pressure, expressed in MPa, a strong overheat-ing of the bed does not occur because of the relatively small content of benzene in the mixture. Instead, the complete hydrogenation of benzene to cyclohexane occurs. Thus, unexpectedly it has been shown that, on nickel catalysts, as opposed to platinum and palladium catalysts, a conversion of benzene of 99.99 %
can be achieved already with small excess of hydrogen, the reaction rate being high. Such a result can be obtained if the partial pressure of hydrogen in the process amounts to even below 0.1 MPa.
Thus, the method of this invention avoids the disadvantages of hitherto known processes. Particularly, it makes possible a complete hydro-genation of benzene with a single evaporation of the raw material and without circulating the gases, whereby there are no limitations relating to the upper limit of the process pressure. This enables the process to be conducted at whatever pressure the hydrogen is supplied, and solves the problem of removal of ~ ~137S~(~
cyclohexane vapours from waste gases.
Both catalyst beds can be disposed either in separate reactors or in single reactor, the tubes of` which are filled with both catalysts in a ma~mer such that the reactant mixture passes first through the platinum or palladium catalyst and then through the nickel catalyst.
In the case of employing two reactors, it is preferable to apply in both the same process pressure, differing only by the values of the resistance of flow. Conveniently, the same process temperature can also be employed. Use of boiling water at a pressure of, for instance, 1.0 to 1.5 MPa as cooling water results in the production of heating steam of high quality. The reaction temperature will be equal to 180 to 200 C, not taking into account local over-heating of the bed to a higher temperature.
In an industrial realization of the process of hydrogenating benzene according to the method of the invention, the gases separated after condensing out the cyclohexane vapour can be, as a rule, discharged to the atmosphere.
If, however, in the process hydrogen is employed which contains con-siderable amounts of inert gases, then it is purposeful, but not necessary, to circulate said gases. The circulated amount can be small, since in the process according to the invention the partial pressure of hydrogen in the reactor can amount to for instance 0.1 MPa, whereas in known processes using platinum or palladium catalysts a partial pressure of hydrogen is required generally of above 2.0 MPa.
EXAMPLE I
A reactor built of a tube having a diameter of 32 mm and length of
2 m was filled with nickel catalyst, and then with palladium catalyst.
The nickel catalyst contained 45 % by weight of nickel deposited on A1203. The palladium catalyst contained 0.62 % by weight of palladium deposited ~137~20 also on aluminium oxide. The catalysts are Eormed into pellets having a dia-meter of 5 mm and the same height.
The palladium catalyst was used in amount four times larger than that of the nickel catalyst. A reduction thereof was carried out with hydrogen at a temperature of about 1~0 C. The tube of which the reactor is built was immersed in a liquid bath filled with liquid having a boiling point of 182 C.
Into the reaction system prepared in this way a gaseous mixture of benzene and hydrogen was dosed from above, in a ratio of 3.15 mole of hydrogen per 1 mole of benzene. The reaction mixture, on being passed through the catalysts beds, was cooled with water, in a membrane system as a result of which the condensation of liquid followed, and the non-condensed gases were discharged to the atmosphere.
Cyclohexane was obtained having the content of benzene of below 0.001 %. The non-condensed gas consisted of hydrogen with small admixtures of methane from the content of which it was calculated that about 0.01 % of intro-duced benzene had undergone conversion to methane.
EXAMPLE II
An identical reactor as specified in the foregoing Example, immersed in a liquid bath filled with a liquid having a boiling point of 182 C, was filled with a nickel catalyst, and then with a platinum catalyst. Aluminium oxide was the carrier for both catalysts. The platinum catalyst contained 1 %
by weight of Pt, the nickel catalyst con~ained 45 % by weight of Ni. After having carried out a reduction of the catalysts wlth hydrogen, a gaseous mixture of benzene and hydrogen having the composition as specified in Example I, was passed through both beds. As a result of the reaction cyclohexane was obtained with a co~tent of benzene of below 0.001 %. In the waste gases very small amount of methane was noted, from the quantity of which it was calculated that 0.012 % of introduced benzene had undergone conversion to methane.
The nickel catalyst contained 45 % by weight of nickel deposited on A1203. The palladium catalyst contained 0.62 % by weight of palladium deposited ~137~20 also on aluminium oxide. The catalysts are Eormed into pellets having a dia-meter of 5 mm and the same height.
The palladium catalyst was used in amount four times larger than that of the nickel catalyst. A reduction thereof was carried out with hydrogen at a temperature of about 1~0 C. The tube of which the reactor is built was immersed in a liquid bath filled with liquid having a boiling point of 182 C.
Into the reaction system prepared in this way a gaseous mixture of benzene and hydrogen was dosed from above, in a ratio of 3.15 mole of hydrogen per 1 mole of benzene. The reaction mixture, on being passed through the catalysts beds, was cooled with water, in a membrane system as a result of which the condensation of liquid followed, and the non-condensed gases were discharged to the atmosphere.
Cyclohexane was obtained having the content of benzene of below 0.001 %. The non-condensed gas consisted of hydrogen with small admixtures of methane from the content of which it was calculated that about 0.01 % of intro-duced benzene had undergone conversion to methane.
EXAMPLE II
An identical reactor as specified in the foregoing Example, immersed in a liquid bath filled with a liquid having a boiling point of 182 C, was filled with a nickel catalyst, and then with a platinum catalyst. Aluminium oxide was the carrier for both catalysts. The platinum catalyst contained 1 %
by weight of Pt, the nickel catalyst con~ained 45 % by weight of Ni. After having carried out a reduction of the catalysts wlth hydrogen, a gaseous mixture of benzene and hydrogen having the composition as specified in Example I, was passed through both beds. As a result of the reaction cyclohexane was obtained with a co~tent of benzene of below 0.001 %. In the waste gases very small amount of methane was noted, from the quantity of which it was calculated that 0.012 % of introduced benzene had undergone conversion to methane.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of hydrogenating benzene to cyclohexane in gaseous phase, which comprises passing a mixture of benzene vapour and hydrogen at a pressure of at least 0.5 MPa and a temperature of 100 to 300 °C through two catalyst beds, the first of which contains a supported platinum or palladium catalyst, and the second of which contains a supported nickel catalyst.
2. A method as defined in claim 1, wherein the method is conducted in both beds at approximately similar temperatures and pressures.
3. A method as defined in claim 1, conducted at a temperature of 150 -220 °C
4. A method as defined in claim 1, conducted at a pressure of 1.0 - 2.5 MPa.
5. A method as defined in claim 1, wherein excessive hydrogen and inert gases, on condensing out cyclohexane, are discharged to the atmosphere, or part-ially recycled to the reactor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PLP-219401 | 1979-11-02 | ||
| PL21940179A PL123566B1 (en) | 1979-11-02 | 1979-11-02 | Process for hydrogenation of benzene to cyclohexane |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1137520A true CA1137520A (en) | 1982-12-14 |
Family
ID=19999256
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000363803A Expired CA1137520A (en) | 1979-11-02 | 1980-10-31 | Method of hydrogenation of benzene to cyclohexane |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1137520A (en) |
| DD (1) | DD154013A5 (en) |
| PL (1) | PL123566B1 (en) |
| RO (1) | RO80686B (en) |
| YU (1) | YU41452B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102746087A (en) * | 2012-08-01 | 2012-10-24 | 厦门大学 | Method for preparing cyclohexane by catalyzing and hydrogenising benzene at room temperature |
-
1979
- 1979-11-02 PL PL21940179A patent/PL123566B1/en unknown
-
1980
- 1980-10-30 YU YU278680A patent/YU41452B/en unknown
- 1980-10-31 DD DD22488080A patent/DD154013A5/en unknown
- 1980-10-31 CA CA000363803A patent/CA1137520A/en not_active Expired
- 1980-10-31 RO RO102481A patent/RO80686B/en unknown
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102746087A (en) * | 2012-08-01 | 2012-10-24 | 厦门大学 | Method for preparing cyclohexane by catalyzing and hydrogenising benzene at room temperature |
| CN102746087B (en) * | 2012-08-01 | 2014-07-02 | 厦门大学 | Method for preparing cyclohexane by catalyzing and hydrogenising benzene at room temperature |
Also Published As
| Publication number | Publication date |
|---|---|
| YU41452B (en) | 1987-06-30 |
| RO80686A (en) | 1983-04-29 |
| PL123566B1 (en) | 1982-10-30 |
| DD154013A5 (en) | 1982-02-17 |
| PL219401A1 (en) | 1981-06-05 |
| RO80686B (en) | 1983-04-30 |
| YU278680A (en) | 1982-10-31 |
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|---|---|---|---|
| MKEX | Expiry |